There has been known a hybrid vehicle having an internal-combustion engine (an engine) and an electric motor connected to an electricity storage device. For example, in a hybrid vehicle equipped with a stepped transmission, a low ambient temperature causes the oil temperature of the transmission and the temperature of the electricity storage device to decrease, affecting the gear shifting responsiveness of the stepped transmission and the use of the electric motor in some cases. At the time of shifting the gear, when synchronizing the rotations of the electric motor and rotating members, such as shafts and gears, which constitute the transmission, with the rotational speeds corresponding to the transmission ratio of a transmission stage, completing a gear shift requires predetermined time due to the inertial moments of the rotating members.
As an example, therefore, a controlling device of a vehicle drive apparatus, which restricts transmission stages when an extremely low temperature state is detected, has been disclosed in patent document 1 as a technique for improving the gear shift responsiveness at an extremely low temperature, such as 30 degrees below zero. In this device, the transmission ratios on a high speed end of the stepped transmission is prohibited, whereas a transmission ratio on a low speed end is selected to increase the numbers of revolutions (rotational speeds) of the rotating members constituting the transmission so as to accelerate a rise in the oil temperature of the transmission, thereby improving the gear shift responsiveness.
Further, patent document 2 discloses, as a technique for increasing the temperature of an electricity storage device, a controlling device of a vehicular battery. When a high possibility of an extremely low temperature state is predicted, the controlling device carries out control to increase the charge amount of the electricity storage device (battery) and then, in the case where the temperature of the battery is a predetermined temperature or lower, the battery is discharged to accelerate internal heat generation, thus increasing the temperature of the battery.